“The staff is devastated by the loss,” he added. “He was a friendly, playful lion.”

The zoo is launching an investigation.

A zoo Facebook post said that Nyack “was a magnificent lion and he will be greatly missed.”

He was described on the zoo’s web page as “very vocal and laid back,” while Zuri was described as a “protective mother.”

There was an outpouring of grief and support for zookeepers over the death of the big cat, clearly a favorite of zoo visitors. Several Facebook comments were posted by people who cared for Nyack as a cub in San Diego. He was on loan to the Indianapolis zoo from California.